EnthalpyQuestion 7

\ce{XY2 -> X + Y2}

The equation above represents the decomposition of a compound $\ce{XY2}$ . The diagram below shows two reaction profiles (path one and path two) for the decomposition of $\ce{XY2}$ .

Which of the following best describes the flow of heat when 1.0 mol of $\ce{XY2}$ decomposes?

50 kJ of heat is transferred to the surroundings.

50 kJ of heat is transferred from the surroundings.

100 kJ of heat is transferred to the surroundings.

100 kJ of heat is transferred from the surroundings.

Approach

Path one shows the reaction as it normally occurs. Path two shows the same reaction in the presence of a catalyst. The net change in potential energy is the same in both cases. The potential energy of the system increases by $\pu{50 kJ/mol_{rxn}}$ , indicating that $\pu{50 kJ}$ of energy was transferred from the environment to the system.